1. Technical Field
The present invention relates to a method of detecting faults in printed circuit boards, especially, to a method of detecting faults in holes of printed circuit boards.
2. Discussion of Related Art
Recently, as the electronic appliances are becoming smaller in size and diversified in function, printed circuit boards (PCBs) widely used in such electronic appliances are required to have high circuit density and reliability.
In order to ensure that printed circuit board can perform its intended function, PCBs must be tested after manufactured. There may be various faults in the printed circuit boards, for example, impurity, over-etching and disconnection. Faults in transmission lines can be easily observed in a telescope or by an automatic optical inspection (AOI) apparatus, however, faults in holes can not be directly observed, it is difficult to detect faults in various holes.
Therefore, there is a desire to develop a method suitable for detecting faults in various holes.